Ozone, which causes photochemical smog, is produced by a photochemical reaction of HC and NOx contained in exhaust gases from vehicles and factories, Therefore, reducing the amount of emissions of BC and NOx from vehicles is an efficient way to suppress the production of ozone and the occurrence of photochemical smog. Also, purifying ozone in the atmospheric air directly can be one of the ways to prevent the occurrence of photochemical smog. By purifying ozone as a product as well as reducing the amount of emissions of BC and NOx as reactants, the occurrence of photochemical smog can be prevented more effectively. In this respect, an vehicle including an air purification device for vehicles capable of directly purifying ozone in the atmospheric air has been put into practical use in some places including California in the United States of America. This air purification device for vehicles, specifically, is called a DOR (Direct Ozone Reduction) system.
For example, Patent Literature 1 discloses a DOR system in which a metal oxide such as manganese dioxide is supported by an on-vehicle component. An on-vehicle component such as a radiator is disposed at a spot in contact with atmospheric air during travel of the vehicle, and manganese dioxide has a function of converting ozone contained in the air into other substances such as oxygen, and purifying ozone. Therefore, according to the DOR system disclosed in Patent Literature 1, ozone in the atmospheric air can be directly purified during travel of the vehicle.
For example, Patent Literature 2 discloses a devise for vehicles which includes shutters disposed in the front of a radiator and driven to be opened and closed by an actuator, and controls the actuator so that the shutters close when engine coolant temperature is low. When the atmospheric temperature is low in cold climates and elsewhere, coolant temperature is disturbed to rise. So, if the shutters are closed, then room temperature in a vehicle can be raised earlier and warming-up time can be shortened.